|
|
| Line 1: |
Line 1: |
| {{multiple issues|
| | They enchant various features like resistant to corrosion, high performance, and low in maintenance.<br>Yet although there are some stinkers, the schedule features some perfectly fine collections; a Russian reality show winner named Dmitry Sholokhov presents a slickly produced commercial offering, while a Georgian named Ria Keburia goes for entertainingly impractical geisha shoes, orange peel effect halo hats and elaborately folded black dresses. Between shows the Mange teems with locals not nearly as well dressed as the It girls, but all terribly enthusiastic about being photographed with a new Mercedes Benz, or the girls in ballgowns promoting wool cleaner who roam the room.<br>http://www.geneseecancerassistance. If you have any concerns about where by and how to use [http://www.restaurantcalcuta.com/outlet/ugg.asp Cheap Uggs Boots], you can get in touch with us at the web-page. com/sale/uggs.asp?p=111 <br /> http://www.geneseecancerassistance.com/sale/uggs.asp?p=76 <br /> http://www.geneseecancerassistance.com/sale/uggs.asp?p=92 <br /> http://www.geneseecancerassistance.com/sale/uggs.asp?p=18 <br /> http://www.geneseecancerassistance.com/sale/uggs.asp?p=121 <br /> <br>http://indico.ifca.es/e-ciencia/index.php/Warning:_These_3_Mistakes_Will_Destroy_Your_Bags_Outlet<br>http://world-forums.site90.net/member.php?action=profile&uid=2166 |
| {{lead too short|date=July 2012}}
| |
| {{underlinked|date=December 2012}}
| |
| {{Orphan|date=December 2012}}
| |
| }}
| |
| [[Concrete]] is a brittle material and can only withstand small amount of tensile [[Deformation_(mechanics)#Engineering_strain|strain]] due to [[Stress (mechanics)|stress]] before cracking. When a [[reinforced concrete]] member is put in tension, after cracking, the member elongates by widening of cracks and by formation of new cracks.
| |
| | |
| [[File:Formation of internal cracks.jpg|thumb|upright=1.35|Figure 1 Formation of internal cracks]]
| |
| | |
| Ignoring the small elastic strain in the concrete between the cracks, we can relate the crack width to the strain of the member by:
| |
| :<math>{w}_{m}= \epsilon_{cf}s_m</math>
| |
| | |
| ==Spacing of Primary cracks==
| |
| Primary cracks (Figure 1) form when the [[tensile stress]] at the outer surface of the concrete reaches the tensile strength of concrete. When a primary crack forms, the concrete in the vicinity of the crack is relieved of any tension, resulting in a stress free zone near the crack.
| |
| | |
| ==CEB-FIP code expressions for crack spacing and crack widths==
| |
| In the CEB-FIP Code the following expression is used to account for the average crack spacing:
| |
| | |
| :<math>s_m = 2(c + \frac{s}{10}) + k_1k_2\frac{d_b}{\rho_{ef}}</math>
| |
| where
| |
| :<math>c</math> = clear concrete cover | |
| :<math>s</math> = maximum spacing between longitudinal reinforcing bars (shall not be taken greater than <math>15d_b</math>)
| |
| :<math>d_b</math> = bar diameter | |
| :<math>\rho_{ef}</math> = <math>A_s/A_{ce f}</math>
| |
| :<math>A_s</math> = area of steel considered to be effectively bonded to the concrete | |
| :<math>A_{ce f}</math> = area of effective embedment zone of the concrete wehre the reinforcing bars can influence the crack widths. The effective embeddment zone is the area of concrete around the reinforcing bar at the distance of 7.5 bar diameter
| |
| :<math>k_1</math> = coefficient that characterizes bond properties of bars
| |
| ::<math>k_1</math> = 0.4 for deformed bars
| |
| ::<math>k_1</math> = 0.8 for plain bars | |
| :<math>k_2</math> = coefficient to account for strain gradient
| |
| ::<math>k_2 = 0.25(\epsilon_1+\epsilon_2)/2\epsilon_1</math> (e1 and e2 = the largest and the smallest tensile strains in the effective embedment zone)
| |
| | |
| ==Crack spacing of inclined cracks==
| |
| According to the [[Modified Compression Field Theory]] (MCFT), the spacing of inclined cracks in reinforced concrete will depend upon the crack control characteristics of both the longitudinal and the transverse reinforcement. It is suggested that the spacing is taken as:
| |
| | |
| :<math>{s}_{m\theta}=1/(\frac{sin\theta}{s_{mx}} + \frac{cos \theta}{s_{mv}})</math>
| |
| | |
| Where <math>s_{mx}</math> is the average crack spacings that would result if the member was subjected to longitudinal tension while <math>s_{mv}</math> is the average crack spacing that would result if the member was subjected to a transverse tension.
| |
| | |
| These crack spacings can be estimated from the CEB-FIP Code crack spacing expression above.
| |
| | |
| ==Crack spacing in shear areas==
| |
| The above CEB expression was intended to calculate crack spacings on the surface of the member. Crack spacings become larger as the distance from the reinforcement increases. For this case, it is suggested to use the maximum distance from the reinforcement, instead of cover distance c (Collins & Mitchell). Thus, for the uniform tensile straining the above CEB expression is modified to:
| |
| | |
| :<math>s_{mx} = 2(c_x + \frac{s_x}{10}) + 0.25k_1\frac{d_{bx}}{\rho_{x}}</math> | |
| | |
| :<math>s_{mv} = 2(c_v + \frac{s}{10}) + 0.25k_1\frac{d_{bv}}{\rho_{v}}</math>
| |
| | |
| The above equations are suggested for better approximation of crack spacings in the shear area of the beam.
| |
| | |
| ==References==
| |
| * {{cite book|last=Collins & Mitchell|title=Prestressed Concrete Structures|year=1997|publisher=Response Publications|location=Canada|isbn=0968195806|pages=152, 349}}
| |
| | |
| * {{cite book|last=CEP-FIP|title=Model Code for Concrete Structures: CEP-FIP International Recommendations|year=1978|publisher=Comite Euro-International du Beton|location=Paris|pages=348}}
| |
| | |
| [[Category:Concrete]]
| |
They enchant various features like resistant to corrosion, high performance, and low in maintenance.
Yet although there are some stinkers, the schedule features some perfectly fine collections; a Russian reality show winner named Dmitry Sholokhov presents a slickly produced commercial offering, while a Georgian named Ria Keburia goes for entertainingly impractical geisha shoes, orange peel effect halo hats and elaborately folded black dresses. Between shows the Mange teems with locals not nearly as well dressed as the It girls, but all terribly enthusiastic about being photographed with a new Mercedes Benz, or the girls in ballgowns promoting wool cleaner who roam the room.
http://www.geneseecancerassistance. If you have any concerns about where by and how to use Cheap Uggs Boots, you can get in touch with us at the web-page. com/sale/uggs.asp?p=111
http://www.geneseecancerassistance.com/sale/uggs.asp?p=76
http://www.geneseecancerassistance.com/sale/uggs.asp?p=92
http://www.geneseecancerassistance.com/sale/uggs.asp?p=18
http://www.geneseecancerassistance.com/sale/uggs.asp?p=121
http://indico.ifca.es/e-ciencia/index.php/Warning:_These_3_Mistakes_Will_Destroy_Your_Bags_Outlet
http://world-forums.site90.net/member.php?action=profile&uid=2166